Copper thallium and lead halide and pseudohalides photosoluble crystals



United States Patent Ofifice 3,377,169 COPPER THALLIUM AND LEAD HALIDE AND PSEUDOHALIDES PHOTDSOLUBLE CRYSTALS Ralph Kingsley Blake, Westfield, N.J., assignor to E. I. du Pont de Nemours and Company, Wihnington, Del., a corporation of Delaware No Drawing. Filed Mar. 30, 1965, Ser. No. 444,022 12 Claims. (Cl. 9688) ABSTRACT OF THE DISCLOSURE Photosoluble crystals of copper, thallium and lead halides and pseudohalides,

(a) Said crystals being characterized by having the surfaces of the metal compound reacted with a small amount of an organic salt-forming compound, e.g., a mercaptan or a selenomercaptan;

(b) The modified crystals dissolving more slowly in sodium thiosulfate solution than unmodified crystals, and

(c) Said salt being less soluble in water than the corresponding chloride of copper, thallium or lead.

This invent-ion relates to photography and more particularly to new image-yielding photographic compositions and to photographic elements embodying such compositions. It further rel-ates to new and useful processes for use of such compositions and elements.

A new type of photographic process has been described in Blake, LUIS. Patent 3,155,507, Nov. 3, 1964. The novel process of this patent, characterized as photosolubi-lization requires the use of a specially prepared silver halide emulsion layer containing a stipulated amount of an organic compound which modifies the silver halide solubility so that in a solution of a conventional silver halide solvent, said organic compound causes the silver halide grains to dissolve at a rate markedly slower than normal. The element is given an imagewise exposure and the exposed area can then be fixed conventionally to yield a positive, silver halide image (the silver halide remaining undissolvedin the unexposed areas). As an optional additional processing step, the silver halide image may be intensified, e .g., by reduction, to convert it into a black, metallic silver image.

It is an object of this invention-to provide newphotographic non-silver halide'compositions, layers, and elements bearing such layers. Another object is to provide photographic layers and elements that are adapted for versatile processes for forming images therein. A further object is to provide simple processes for making these compositions. Still further objects will be apparent from the following description of the invention.

The photosoluble, photographic composition ofthis invention comprises, before imagewise exposure to radiation, crystals of a metal compound the cation of which is anion of a metal selected from the class consisting of copper, thallium and lead, and theanion is an anion selected from the group consisting of the halides and the pseu'dohalides;'said'crystals being characterized by having associated therewith a copper," thallium, or lead salt of an organic salt-forming compound, 's-aid' crystals dissolv ing markedly more slowly in aqueous sodium thiosulfate solution, not so associated with the salt, and said compound being further characterized in that the salt which it forms with the copper, thallium, or lead cation of said crystals is less soluble in water at 25 C. than the corresponding chloride of said copper, thallium or lead cation.

The organic salt-forming compounds disclosed in the examples are especially effective in reacting with the copata predetermined pH,than crystals 3,377,169 Patented Apr. 9,

per, thallium or lead compounds to cause them to dissolve more slowly in 10% The crystals reacted with these organic compounds are also photosoluble, i.e., when treated with aqueous thi-osulfate solution the irradiated crystals will dissolve more rapidly than non-irradiated crystals. Representative compounds include the mercaptans, a substituted thiourea (which may be considered as a mercaptan in its enol form), and a compound containing a nitrogen atom in its heterocyclic ring. Many other specific organic mercaptans such as those disclosed in the above Blake patent US. 3,155,507 can be used in accordance with this invention for modifying the solubility characteristics of the metal salt, i.e., copper, thallium and lead crystals. In addition to mercaptans, the selenium analogues (wherein the sulfur atom is replaced by a selenium atom) exhibit essentially equivalent effectiveness. Organic salt-forming compounds that satisfy the screening test procedures (namely Test A and Test B of Blake U.S. P. 3,155,507, can be used in accordance with this invention.

Thus, the effective organic salt-forming compounds must meet the condition that, when admixed in a suitable quantity with an aqueous silver chlorobromide (70/30 mole percent) gelatin dispersion containing 10 g. of gelatin per mole of Ag and .57 mg. of Ag per ml., and said silver chlorobromide dispersion is treated with 10%, by weight, aqueous sodium th-iosu'lfate (so that the resulting mixture contains 0.29 mg. of silver and mg. of sodium thiosulfate), at least three times the amount of'si'lver chlorobromide remains un-dissolved as in a similar dispersion successively treated with 5%, by weight, aqueous sodium hyp'ochlorite and 10%, by weight, aqueous'sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver, 25 mg. of sodium hypochlorite and 100 mg. of sodium th-io'sulfat-e), after vigorous agitation of both dispersions for 30 seconds at 25 C.

In making the photographic layers and elements of this invention, preferably the photosoluble crystals are dis-. persed in an aqueous solution of a water-permeableorganic colloid, e.g., gelatin, to form a photographic emulsion. The copper, thallium, or lead salt is made from the selected organic salt-forming compound that is added to the photographic emulsion while the latter is in the liquid state or the emulsion may be coated on a suitable support and the resulting element bathed or impregnated with a solution, e.g., an ethanolic solution of the organic compound. The desired amount of the organic compound in the light-sensitive emulsion may vary with a number of factors such as the size of the metal salt crystal (and thus the surface area of the crystal per mole). Generally the organic compound is used in a range from 0.3 to 1.5; gram per mole of the metal salt crystal and preferably from 0.4 to 1.2 gram per mole.

The ratio of the treated (photosoluble) metal salt crystals to gelatin can vary over a moderate range, e.g., 1:3 to 10:1 depending upon the particular organic-compound and crystal. Also, it is possible to treat a layer of the metal salt crystals on the base material in the essential absence of a binder, e.g., a layer prepared by chemi cal or vacuum deposition. 7 An image-forming process of the invention, ingdirect-positive images, comprises I '(a) Exposing, imagewise, to actinic radiation :1 photo: sensitive layer comprising metal salt crystals treated with the organic salt-formingcompound as described above,

(b) Treating the exposed layer in a silver halide solvent to remove the soluble metal salt and associated material in the exposed image areas, thus forming a direct-positive image of the remaining undissolved, treated (photosoluble) crystals.

Optimally, the image may be washed, e.g., with Water.

for producaqueous sodium thiosulfate.

If desired, the positive image may be viewed directly, e.g., by projection (if on a transparent support) or it may be intensified, e.g., by dye mordanting, reduction to a metallic image, or chemical reaction to produce a more opaque or light'absorbing image such as conversion to a black sulfide, or as in the case of CuSCN, reaction with silver nitrate solution to yield a black silver image.

' The imagewise solution of the exposed photosoluble crystal/organic compound stratum may be effected by the solutions of the silver halide solvents commonly used as photographic fixing agents e.g., sodium thiosulfate, potassium thiosulfate, and ammonium thiosulfate.

The dispersed metal salt crystals treated with an appropriate amount of a suitable organic compound as described above, are affected by exposure of actinic radiation, e.g., ultraviolet, visible, infrared, X-radiation, etc., to such an extent that at least of the less soluble crystals remain when 90% of the more soluble crystals dissolve when treated in 10% by weight aqueous sodium thiosulfate solution.

Suitable elements in this invention can be prepared by bathing a film comprising a stratum of metal salt crystals, as described above in a solution of an appropriate organic compound. In this embodiment, the metal salt crystals near the surface of the coated emulsion stratum are in contact with a higher concentration of the organic compound. Crystals farther from the surface are treated with less of the organic compound and, if the rate of diffusion is sufficiently slow, there may be considerably less of the organic compound (even approaching zero) reacting'with the lower than with the surface metal salt crystals. In such elements, satisfactory results can be obtained with only'a fraction, e.g., one-half of the amount of the organic compound theoretically calculated as required to just cover the surface of a mole of the metal salt crystals. This invention will be further illustrated by, but is not intended to be limited to, the following examples.

EXAMPLE I Ml. Photographic gelatin (2.5% by weight aqueous solu- .tion) 1 Potassium bromide (0.1 M) 5.1

Thallous nitrate (0.1 M) 5 Solution B was added to Solution A with stirring. To the resulting suspension of thallous bromide, 5 g. of solid Na S O were added. The TlBr dissolved rapidly yielding a clear solution.

A similar suspension of TlBr was prepared, to which was added 05ml. of a 0.12% by weight ethanolic solution of 2-mercapto-4-phenylthiazole. Five grams of solid Na S O wereagain added but this time the TlBr did not dissolve to any visible extent. When irradiated by a high intensity, tungsten filament, incandescent lamp (General Electric Reflector Photoflood lamp, ASA No. PH/RFL2) at a distance of 6 inches, the TlBr dissolved in less than seconds, yielding a clear solution. Thus, it was demonstrated that TlBr crystals can be made to dissolve much more slowly (so slowly as to appear visibly insoluble) in a sodium thiosulfate solution when said crystals are in association with Z-mercapto-4 phenylthiazole. It was further demonstrated that the effect of the mercaptan is overcome by the action of light, a phenomenon called photosolubilization."

Cupric sulfate (1 M) 5 Potassium iodide (1.2 M) 8.5

Solution B was added to Solution A with stirring. The white, fine precipitate of cuprous iodide that formed in accordance with the equation given below, was filtered and washed with water to remove reaction by-products:

The precipitate was washed from the funnel with 50 ml. of water to yield a CuI suspension.

To 10 ml. of this suspension, 3 ml. of 0.5 M Na S O were added. The CuI dissolved immediately, leaving a clear solution.

To 10 ml. of this suspension, 0.2 ml. of 1% 2-mercapto- 4-phenyl thiazole were added. The CuI did not dissolve to any visible extent when 3 ml. of 0.5 M Na S O were added. When this suspension was irradiated by the incandescent lamp of Example I at a distance of 6 inches, it became clear in one minute.

EXAMPLE III Fifty ml. of 0.1 M sodium fluoride and 50 ml. 0.1 M potassium chloride were mixed with 25 ml. water. To this solution 50 ml. of 0.2 M lead nitrate were added. A white, voluminous precipitate of lead chlorofiuoride (PbClF) formed.

To 25 ml. of this suspension, 10 ml. of 0.5 M Na S O were added. Solution was complete and immediate.

To 25 ml. of this suspension, 1 ml. of 0.1% Z-mercapto- 4-phenyl thiazole was added. The precipitate was insoluble when 10 ml. of 0.5 M N21 S O was added. On irradiating with the incandescent lamp of Example I at a distance of 6 inches, the precipitate dissolved in a few seconds.

Example IV The following solutions were prepared:

Solution A H O ml 50 NaHSO g 0.5 NH SCN (2 M) ml 2.5

Solution B CuSO, (1 M) ml 5 When Solution B was added to A, a white precipitate of CuSCN formed by the reaction:

To 5 m1. of the resulting suspension, 5 ml. of a commercial photographic fixing solution of the following formulation were added with a resultant, essentially instantaneous dissolution of said suspension:

To another 5 ml. portion of the CuSCN suspension, 0.5 ml. of 0.1% Z-mercapto-4-phenylthiazole was added. The precipitate did not dissolve to any visible extent when 5 ml. of the above commercial fixing solution were added. On irradiating with the incandescent lamp of Example I at a distance of 12 inches, the solution became clear in less than 30 seconds.

Example V The following solutions were prepared:

Solution A V t Distilled water ml 820 Ammonium thiocyanate g 63.9 Sodium bisulfite (NaHSO g 90 Solution B A Distilledwater" ml 800 CUSO4=5H2O g.

Solution B was added to Solution A with constant stirring while a voluminous white precipitate of CuSCN formed. An additional g. of solid NaHSO were then added, and the mixture stirred for /2 hour. The precipitate was collected ona medium porosity fritted glass funnel and Washed 3 times with 100 ml. portions of water.

The washed precipitate was added to 540 g. of an aqueous 8% solution of photographic gelatin, and the mixture stirred at 120 F. for /2 hour.

, To 200 g. of the resulting CuSCN emulsion, 60 ml. distilled water were added, and-this composition coated at 95 F. on subbed polyethylene terephthalate film base made according to Example IV of Alles, US. Patent 2,779,684, to yield a dried film'with a CuSCN coating weight of 100 mg./dm.

The following insolubilizing solution was prepared:

7 M1. 1.2% by weight ehtanolic solution of 2-mercapto-4- phenylthiazole Solution [1 g. of dye (given below) dissolved in 2000 m1. acetone] 25 Ethanol 244 Distilled water 175 Dye: HzC-S S CH3 l H2CN fi NC2H5 Example V was repeated except for replacing 2-mercapto-4-phenylthiazole' with lauryl -mercaptan (l-dodecanethiol). A direct positive image was again obtained.

Four other samples of a coating of a CuSCN emulsion,

prepared as in Example V, were dipped in various insolubilizing solutions in which the 2-mercapto-4-phenylthiazole of that example was replaced with an equivalent amount of the following mercaptans:

(a) thiophenol V h (b) 2-rnercaptobenzothiazolei (c) 1-phenyl-S-mercaptotetrazole (d) Z-naphthalenethiol After exposure and treatment in the photographic fixing solution as described in Example V, direct positive images were obtained in all four coating samples.

Example VII A sample of a coating of a CuSCN emulsion, prepared as in Example V, was dipped in insolubilizing solution in which the Z-mercapto-4-phenylthiazole of that example was replaced with an equivalent amount of 6-nitrobenzimidazole and the solution raised to pH above 8.0 by the addition of NaOH. After exposing as in Example 6 V, the coating was treated for 3 minutes in a 0.5 Na S O solution which had been adjusted to a pH of 8.5 by addition of NaOH. A direct positive image was obtained.

' Example VIII A lead iodide emulsion was made by adding an aqueous lead nitrate solution to an aqueous gum arabic solution containing potassium iodide as described in Example I of Weyde, US. 2,084,420. The thioacetamide and glycerine called for in that example were omitted. Following 3 washes in alcohol the emulsion precipitate was redispersed in a 5% by weight aqueous gelatin solution in the ratio of 1 part gelatin to 4 parts of the precipitate on a weight basis. The emulsion was then melted and coated at F. and 25 ft. per minute on the film base described in Example V. This lead iodide coating was overcoated with the insolubilizing solution of Example V at 15 ft. per minute and dried in air.

A specimen of this coating was wet with water, squeegeed, and exposed for /2 minute through a line negative by the incandescent lamp of Example I at a distance of 12' inches. Treating for 30 seconds in a solution containing 128 g. N21 S O per liter of H 0 gave a direct positive lead iodide image.

Example IX Example VIII was repeated except the 2-mercapto-4- phenylthiazole was replaced by a-naphthylthiourea in equivalent quantity and similar results were obtained.

In place of part of the gelatin, other gelatin-compatible natural or synthetic water-permeable organic colloid binding agents can be used and in some cases the agents can be used alone. Such agents include waterpermeable or water-soluble polyhydrolyzed polyvinyl acetates, polyvinyl ethers and acetals containing a large number of intralinear CH CHOH groups, hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compound such as maleic anhydride, acrylic and methacrylic acid esters and styrene. Suitable such colloids of the last-mentioned type were disclosed in US. Patents 2,276,322; 2,276,323 and 2,297,- 866. The useful polyvinyl acetals include polyvinyl acetaldehyde acetal, polyvinyl butyraldehyde acetal and polyvinyl sodium o-sulfobenzaldehyde acetal. Other suitable colloid binding agents which can be used include the poly-N-vinyllactams of Bolton US. Patent 2,495,918, various polysaccharides, e.g., dextran, dextrin, etc., the hydrophilic copolymers in- Shacklett, US. Patent 2,833,- 650, hydrophilic-cellulose ethers and esters, and polymersof acrylic and methacrylic esters and amides.

The emulsions can be coated on any suitable support, e.g., cellulose esters, cellulose mixed esters; superpolymers, e.g., .poly(vinyl chloride co vinyl acetate); polyvinyl acetals, butyrals; polystyrene; polyamides, e.g., polyhexamethylene adipamide; polyesters, e.g., polycar- 'bonates, polyethylene terephthalate/isophthalate, esters formed by condensing terephthalic acid and its derivatives, e.g., dimethyl terephthalate with propylene glycol, diethylene glycol, tetramethylene glycol or cyclohexane-l',

'4 dimethanol (hexahydro-p-xylene dialcohol); paper,

metal, glass, etc.

The novel photographic compositions of this invention-have numerous advantages. An important advantage is the simplicity of their preparation. Although no advantages in quality have been demonstrated over the related silver halide systems, it is obvious that many nonsilver halide systems can be manufactured much more inexpensively because of the relatively lower prices of the light-sensitive salts utilized. In many instances, the elements of this invention provide photographic images of very high covering power which is a commercial advantage.

Another advantage of this invention is that it provides new elements for forming photographic images that do not require special equipment but instead can be used 7. with conventional equipment and apparatus. A further advantage is that the elements can be used successfully by photographic technicians and photographers of ordinary skill. Still additional advantages will be apparent from the above description of the invention.

I claim:

1. Photosoluble crystals of a metal compound the cation of which is an ion of a metal selected from the group consisting of copper, thallium and lead, and the anion is an ion selected from the group consisting of the halides and pseudohalides;

(a) said crystals being characterized by having associated therewith a salt selected from the group consisting of copper, thallium and lead salts of an organic salt-forming compound selected from the group consisting of organic mercaptans and organic selenomercaptans by reaction of the surfaces of the crystals of the metal compound with 0.3 to 1.5 grams of said organic saltforming compound per mole of the metal compound, said salt-forming compound having the properties:

that when admixed with an aqueous silver chlorobromide (70/30 mole percent) gelatin dispersion containing 10 g. of gelatin per mole of Ag and .57 mg. of Ag per ml., and said silver chlorobromide dispersion is treated with 10%, by weight, aqueous sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver and 100 mg. of sodium thiosulfate), at least three times the amount of silver chloride remains undissolved as compared with a similar dispersion successively treated with by weight, aqueous sodium hypochlorite and by weight, aqueous sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver, mg. of sodium hypochlorite and 100 mg. of sodium thiosulfate), after vigorous agitation of both dispersions for seconds at 25 C.

(b) said crystals dissolving markedly more slowly in 10% aqueous sodium thiosulfate solution, at a predetermined pH, than crystals not so associated with the salt; and

(c) said compounds being further characterized in that the salt it forms with said cation is leSs soluble in water at 25 C. than the corresponding chloride of said cation.

2. A composition according to claim 1 wherein said organic salt-forming compound is a mercaptan.

3. A composition according to claim 1 wherein said organic salt-forming compound is 2-mercapto-4-phenylthiazole.

4. Acomposition according to claim 1 wherein said organic salt-forming compound is a thiourea.

5. A composition according to claim 1 wherein said organic salt-forming compound is a-naphthylthiourea.

6. A photographic element comprising a support bearing a layer of a composition as defined in claim 1.

7. A photographic element comprising a layer of a Water-permeable organic colloid binding agent containing before imagewise exposure to actinic radiation as the sole radiation-sensitive material, photosoluble crystals of a metal compound the cation of which is an ion of a metal selected from the group consisting of copper, thallium and lead and the anion is an anion selected from the group consisting of the halides and pseudo halides;

(a) said crystals being characterized by having associated therewith a salt selected from the group consisting of copper, thallium and lead salts of an organic salt-forming compound selected from the group consisting of organic mercaptains and organic selenomercaptans by reaction of the surfaces of the crystals of the metal compound with 0.3 to 1.5 grams of said organic salt-forming compound per mole of the metal compound, said salt-forming compound having the properties:

that when admixed with an aqueous silver chlorobromide (/30 mole percent) gelatin dispersion containing 10 g. of gelatin per mole of Ag and .57 mg. of Ag per m1., and said silver chlorobromide dispersion is treated'with 10%, by weight, aqueous sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver and mg. of sodium thiosulfate), at least three times the amount of silver chloride remains undissolved as compared with a similar dispersion successively treated with 5%, by weight, aqueous sodium hypochlorite and 10%,

' by weight, aqueous sodium thiosulfate (so that the resulting mixture contains 0.29 mg. of silver, 25 mg. of sodium hypochlorite and 100 mg. of sodium thiosulfate), after vigorous agitation of both dispersions for 30 seconds at 25 C.;

(b) said crystals dissolving markedly more slowly in 10% aqueous sodium thiosulfate solution, at a predetermined pH, than crystals not so associated with the salt; and

(c) said compound being further characterized in that the salt it forms with said cation is less soluble in water at 25 C. than the corresponding chloride of said cation.

8. An element according to claim 7 wherein said colloid is gelatin.

9. An element according to claim 7 wherein said organic salt-forming compound is a mercaptan.

10. An element according to claim 7 wherein said organic salt-forming compound is 2-mercapto-4-phenylthiazole.

11. An element according to claim 7 wherein said organic salt-forming compound is a tliiourea.

12. An element according to claim 7 wherein said organic salt-forming compound is a-naphthylthiourea.

References Cited UNITED STATES PATENTS 3,155,507 11/1964 Blake 9694 3,175,908 ,3/1965 Schneider 9638 FOREIGN PATENTS 968,141 8/1964 GreatBritain.

NORMAN G. TORCHIN, Primary Examiner.

C. E. DAVIS, Assistant Examiner. 

